Tearing resistance of heterogeneous interface region of a dissimilar metal weld characterised with sub-sized single edge bend specimens

Abstract

Determination of tearing resistance of heterogeneous dissimilar metal welds (DMW) that are critical structures of pipes in nuclear power plants (NPPs) is important in assessment of the structural integrity. Currently, tearing resistance of heterogeneous materials is determined by standards developed for homogeneous materials. The fracture behaviour of heterogeneous materials differs from fracture behaviour of homogeneous materials. Thus standards developed for homogeneous materials are not necessary directly applicable to heterogeneous materials. To develop a standard for heterogeneous materials the current level of knowledge of fracture behaviour in heterogeneous specimens needs to be increased. To enhance the knowledge of fracture in heterogeneous materials tearing resistance of 10×10×55 mm3 and 10×20×100 mm3 single edge bend (SE(B)) specimens extracted from a NPP ferrite-austenite DMW were measured. The specimens were extracted at three different crack locations in a region close to the fusion line between ferritic steel and weld metal of the DMW. As tearing resistance curves of the two specimen geometries are compared toughness and scatter varies, which can be explained by differing crack location with respect to the fusion line. However, the effect of crack location on tearing resistance was not microstructurally quantified, but the qualitative analysis of crack location done in this work implies that a standard developed for heterogeneous materials shall contain guidelines on characterisation of crack location.